Fluid strainer or filter



Feb. 29, 1944. A. c. HOFFMAN FLUID STRAINER OR FILTER Filed July 5, 1940Patented F eb. 29, 1944 UNITED STATES PATENT OFFICE 4 'Claims.

This invention pertains to filters for fluids for the purpose ofeffecting mechanical separation of solids from fluids or fluids fromfluids, and particularly to a filter in which the separation iseffected'through a filter coil.

The principal object of this invention is to construct a filter coil inthe most inexpensive manner wherein the finished coil in the specificillustration herein will have its several helices provided withsegmental portions of large and small diameters and wherein the largediameter segments are disposed in abutting relationship one above theother and the remaining segmental portions of small diameter beingdisposed in spaced relationship to provide numerous interstices of aminute character through which the fiuid is filtered.

A further object resides in providing a method of obtaining thesegmental interstices in the manufacture of the coil whereby the size ofthe interstices can be readily controlled for various adaptations towhich the filter may be used.

A further object is to provide a casing for receiving the filter coiland in which the latter is held secure and in a fixed predeterminedrelationship, and wherein the numerous helices of the coil are heldunder resilient "axial compression to assure a uniform size of t l efiltering interstices under all conditions.

A further object is to provide a means for thoroughly cleaning the fiter without disassembling or disturbing the filter element ornecessitating the detachment of the filter unit from the device to whichit is applied, and which cleaning operation is accomplished by thesimple expedient of fiuid pressure. In the present disclosure this meansincludes shut-oif valves designed to operate to preclude any sedimentbeing forced back into the discharge and feed lines when in one positionand to prevent leakage through the threaded portions of the valvestructure when in the opposite position.

With the above and other objects in view a preferred embodiment of theinvention selected 1 for the purpose of illustration is shown in theaccompanying drawing in which Fig. 1 shows a longitudinal sectional viewof the filter device embodying/this invention.

Fig. 2 is a transverse sectional view taken on line 2-2 of Fig. 1. I

Fig. 3 is a vertical sectional view through a portion of the filter coilshowing portions of each helix masked preliminary to a platingoperation.

Fig. 4 is a plan view of the same.

Fig. 5 is a similar view to Fig. 3 showing the helices as completed withthe masked sections stripped and further showing the helices incompressed relationship, and

Fig. 6 is a plan view of the same.

Referring now to the drawing wherein like numerals designate like partsthroughout the several views, the numeral I 0 indicates a body or casinghaving a tapering base II and its open and closed by a screw cap orcover [2. A helical 3 wire filter coil I3 is received within the chamberFilter coil construction Th particular manner in which the filter coilis made forms one of the principal features of this invention and a moredetailed description of l the same will be given herewith. The preferredmethod of attaining a difference in the diametrical size of thesegmental portions of the helices in the filter coil I3 is by a platingoperation. Specifically the wire of the coil I3 i preferably of roundcross section, and predetermined po'rtions may be blocked or maskedoif'by a dielectric material, preferably a lacquer, commonly used inplating and indicated by the-numeral |3a in Figures 3 and 4.

In commercial practice the bare wire, either straight or coiled, wouldbe insulated against plating by masking uniformly spaced portions of thewire as shown in Figures 3 and 4 so that the masked portions of 'oneturn of the coil will lie juxtaposed with the correspondingly maskedportions of adjacent coils and the unmasked portions willcorrespondingly align themselves. As shown in Figure 4 it is preferableto mask each individual coil in three equal sections for the reasonhereinafter described, the length of the masked portions beingpreferably longer than the unmasked portions. This sectional masking ofthe coil may be accomplished in several ways. One simple way for thepurpose of illustration would be to use a cylindrical stencillongitudinally slotted at three equally spaced points. This stencilwould have complementary internal and external parts to fit inside andoutside the coil. 'I'hen'by the use of suitable spraying equipment theexposed aligned sections of the coil would be spray coated with lacquerforming the mask l3a.

After this lacquer has dried the coil is placed in a plating bath suchas chromium or the like and the plating material is deposited on theuncoated sections as indicated by the numeral |3b in Figures 5 and 6. Aswill be obvious to those skilled in the art of plating, the thickness ofthe deposit can be closely controlled by adjustment of the electrolyte,current and time. By actual experiment a deposit of three tenthousandths of an inch (.0003") in ten minutes has been secured. Byincreasing or decreasing this time element alone the thickness of thedeposit may be varied and accurately controlled for predetermined sizes.

After the deposit of plating material has been made the mask may readilybe dissolved ed the helices 'by using a suitable solvent. Then, as shownin Figures 5 and 6, by compressing the helices together the thickerplated sections |3b of the wire where the plating has taken place willabut and carry the compressing load leaving the unplated sections spacedapart by a distance equal to twice the deposit of plated material. Thisspacing forms the fine interstices |3c heretotore mentioned.

From the foregoing description it is seen that the main part of thefilter is a single piece of wire easily and cheaply manufactured toprecise dimensions. The coils are plated at three sections because thisis the geometrically correct method to carry the compressing forceacting on the coil.

Other methods of efiecting this 'three point plating will be obvious.Furthermore it is possible to reduce the diameter of the wire byacidetching. In this case an acid resistant lacquer is applied at threeplaces on each helix and the unprotected sections of the wire arereduced in diameter by action of the acid. Then by dissolving oil thelacquer and compressing the spring the unetched sections will abut andcarry the load with the interstices therebetween in a manner identicalto the plating method.

Filter casing assembly to facilitate the assembly and effect a tightengagement with the adjacent surrounding helices of the coil I3. Theupper plug i5 is supported against the inner face of the cap l2 and isformed with a relatively large peripheral flange |5a against which theuppermost helix of the coil i3 abuts as a stop. The outer edge of theflange |5a further serves as a sealing washer between the edge of thecasing i0 and the cover i2 when the latter is assembled and tightlyscrewed into position by threads l1. The lower plug I6 is provided witha relatively smallerperipheral flange |6a for supporting the lowermosthelix of the coil I3 and the entire plug is supported by a metal backingplate l8 having a central countersunk recess IQ for the reception of thesmaller end of a conical compression spring 20. The large end of thespring 20 seats in a complementary recess ||a formed in the base H ofcasing Ill. The spring 20 is sufficiently strong not only to support thefilter coil assembly (parts l3, l5, l6 and I8) but also to keep all theindividual helices of the coil |3 tightly compressed with the adjacentplated sections |3b of each helix tightly abutting against each otherand carrying the full weight of the compression load and assuring thepredetermined spacing of the adjacent helices.

The fluid to be filtered is directed into the easing in at the basethereof in the customary manner. Specifically the casing base II isformed with a depending boss 2| having a tapped lateral opening 22communicating with a central bore 23 within the boss 2|. An inlet pipenot shown may be connected into the tapped opening 22 in the usualmanner. The fluid that has been filtered through the coil unit, as willbe more fully described in the operation, is directed out through arelatively large opening 24 in the upper plug I5 aligned with a smallbore 25 within an upstanding boss 26 formed as an integral part of thecover l2. A lateral tapped opening 21 connects into bore 25 and asuitable outlet pipe connection may be made into said opening 21 throughwhich the filtrate may be directed back to its source.

' Shut-of valves In order to fulfill another stated object of thisinvention, provision is made to exhaust the fluid in the chamber Ma andclean all deleterious foreign material that may have accumulatedtherewithin. To accomplish such it is necessary to provide two shut-oilvalves, one at each end of the filter generally indicated by numerals 28and 29. stem 30 threadedly engaged in a tapped hole in boss 2| alignedwith the bore 23. The inner end of the stem 30 carries a valve head 3|adapted to engage a valve seat 32 formed at the upper end of bore 23.The sediment that is to be discharged from the filter during thecleaning operation is exhausted through a central passage 33 in stem 30out through a lateral opening 34 intersecting said passage 33. Theoperation of the valve 28 is effected by a nut 35 threaded to the outerend of the stem 30. When the valve 28 is in open or normal operatingposition the valve stem is screwed into its innermost position and thevalve head 3| is removed from the seat 32 by means of the nut 35. Thenut 35 then assumes a position against the face of the boss 2| with asealing washer 36 compressed therebetween to effect a seal. In case thenut fails to operate the stem, a screw drive slot 31 is provided in theouter end of said stem 30.

The upper valve 28 comprises a valve stem 38 threadedly engaged in abushing 39 which in turn is threaded into. the tapped section of alateral valve chamber 40 in boss 26 and communicatin with bore 25. Theinner end of the stem 38 supports a double headed valve 4|, theinnermost inclined face of which seats against a valve seat 42 formed atthe juncture of the'outlet opening 21 and the valve chamber 48 when thevalve is closed for flushing the filter. When the valve is in its normaloperating position the opposite inclined face of the valve head 4| isseated against a valve seat 43 formed at the innermost end of thebushing .39 and prevents any leakage of fluid through the tapped hole ofbushing 39. A washer 44 is interposed between the head end 45 of Thelower valve 28 comprises a valve tral passageway 48 intersecting alateral opening 43 in said stem 33.

Operation In operation the fluid to be filtered enters at the pipeconnection 22 in boss 2|. Valve 28 and valve stem 30 are screwed up intothe boss 2| until washer 36 and nut 35 seat tightly against lower end ofboss 2| sealing the opening 34 against the outside. The fluid istherefore able to enter the casing l and fills up the space |0asurrounding the coil I3. Since the fluid is under pressure it will beforced through the interstices I 30 between the helices. Then it willtravel up through openings 24 and 25. The valve 29 and valve stem 38will be screwed to the position where valve 4| seats against valve seat43. When in this position the outlet connection 21 is open and thefiltered fluid can be returned for further use.

During the passage of the oil through the coil l3 solids larger than theinterstices I30 are trapped on the outside of the coil |3 where theyremain until dislodged by vibration or until they are removed entirelyfrom the filter during the cleaning operation.

To clean the filter both valves 28 and 23 are screwed into positionshown in Figure 1. Fluid pressure is applied at 41 which forces fluidthrough the Openings 48, 49, 40, 25 and 24 to the inside of coil i3.This counter-flow pressure forces the fluid inside the coil l3 outthrough the interstices |3c between the helices carrying with it anyaccumulated solids.

Meanwhile nut 35, washer 36, ,valve stem and valve head 3| have beenscrewed outwardly from the boss 2| of the casing ill until valve head 3|seats tightly against valve seat 32. This opens passageway 33 andlateral opening 34 to the outside and closes pipe connection opening 22.Continued pressure at nipple 41 forces the unfiltered fluids andaccumulated solids out through the valve stem 30 and opening 33 and 34.

When this flushing operation has been completed the valve head 3| isopened until washer 36 and nut seat securely against boss 2| and valve4| is unseated from its seat 42 and seated at its seat 43. The fllter isnow in position to resume its normal function.

From the foregoing, it will be seen that the invention provides a novel,simple and improved fllter which will ably perform the objects set forthand it will be understood that numerous changes, modifications and thefull use of equivalents may be resorted to in carrying out thisinvention, without departing from the spirit and scope of the appendedclaims.

What I claim is:

1. In a filter, a casing having an open end and a including a helicallywound member having spaced deposits of electrodeposited metal of uniformthickness disposed around the circumference of the wire forming each ofthe helices thereof to provide spaced areas of increased cross-sectionand so positioned as to be in abutting relation to the similar depositsupon each of the next adjacent helices when said filter element issubjected to axial compression so as to provide filtering passes betweenadjacent helices, and means having a fluid outlet therethrough forsubjecting the filter element to axial compression and for closing theopen end of the casing to confine the element within the latter.

2. A fllter element of the character described. including a continuousmetalllcfllterelement coiled to provide a plurality of axially aiinedhelices. and spacing members between said helices composed of spaceddeposits of electrodeposited metal of uniform thickness deposited aboutthe circumference of the metal forming said helices to provide spacedareas of greater cross-section than the normal cross-section of thehelices forming the filter element, said spacing members being disposedin abutting relation to the spacing-members on adjacent helices, wherebyto provide filtering passes between each pair of said adjacent helices.

3. A fllter element oi the character described in which the portion ofthe element through which the liquid is filtered is formed by acontinuous metallic member coiled to provide a plurality of juxtaposedconvolutions of said metallic member and spacing members between saidconvolutions composed of spaced deposits of electrodeposited metalforming enlargements on a convolution to provide abutments spaced alongthe metal forming said convolutions and facing the adjacent convolution,said spacing members being so disposed that when the element isassembled, said abutments on juxtaposed convolutions contact and form.filtering passes between adjacent convolutions.

4. In a. filter, a casing having inlet and outlet means for a fluid tobe filtered; an expandable and compressible metallic filter elementdisposed in said casing and providing a fluid passage therebetween, saidfllter element having a member arranged in convolutions having spaceddeposits of electro-deposited metal disposed on the circumference of themember forming each of the convolutions thereof, said deposits providingspaced areas of increased cross-sections and so positioned as to be inabutting relation to the similar deposits upon each of the next adjacentconvolutions when said filter element is subjected to comression so asto provide filtering passes between adjacent convolutions, and means forsubjecting the fllter element to compression to confine the elementwithin said casing spaced therefrom and retained between said inlet andoutlet means.

ALLAN c. HOFFMAN.

